Geometry and the Discrete Fourier Transform

Revised version of a November 2011 Feature Column
on the AMS website. The underlying technologies changed and so tweaks had to be made in
order that it function as intended, and, indeed, how it used to. I kept an
older version if you want to see it.

Note these demonstrations use the Geometer Sketchpad Java applet, so they will
not display in Google's Chrome browser after Version 42, or in any other browser
which does not have a modern Java plugin activated.